Search

The excitation energies of the Be-like ions (4 ≤ Z ≤ 74) doubly excited state 1 s 2 2 p 2 and doubly core-excited state 2 s 2 p 3 are calculated using the multi-configuration Dirac–Hartree–Fock method. The contributions of relativistic effects, Breit interaction, and QED effects to the excitation energies are analyzed and discussed in detail. A reasonable electron correlation model has been constructed using the active set method. The electron correlation and the finite size of the atomic nucleus correction have also been appropriately considered. The calculated results agree with the available theoretical and experimental data. It is found that the contribution of relativistic effects, Breit interaction, and QED effects to the excitation energy becomes significant with increasing Z. The contribution of the relativistic effects reaches about 8.5% at Z=74. The 3 P 0 level of the doubly excited state 1 s 2 2 p 2 is sensitive to the Breit interaction and the QED effects, but these two contributions cancel each other out. For the doubly core-excited state 2 s 2 p 3 , the Breit interaction and the QED effects are almost equally important, and their maximum contribution is about 0.5%. These results are expected to help future experimental and theoretical work. [ABSTRACT FROM AUTHOR]

Based on the fully relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) method and the corresponding program package GRASP2018, a new program for calculating the polarizabilities is developed. As the first application, the static electric-dipole polarizabilities of the ground state 2s21S0 and excited state 2s2p 3P0 of beryllium are calculated. By means of these polarizabilities, the blackbody radiation (BBR) shift of the 2s2p 3P0 → 2s21S0 clock transition is determined. The present results agree very well with other available theoretical results. [ABSTRACT FROM AUTHOR]

The dielectronic recombination of Li-like Xe (2s) ions was studied using the flexible atomic code based on the relativistic configuration interaction method. The resonance energies, radiative and autoionization rates, and resonance strengths were calculated systematically for the doubly excited states (2 p n l )( n = 18−32) and (2 p n′ l )( n′ = 9−27) of Be-like Xe ions. For the higher Rydberg resonance states with n ≥ 33 and n′ ≥ 28, the resonance energies and strengths were obtained by extrapolation based on quantum defect theory. The theoretical rate coefficients, covering the center-of-mass energy range 0-505 eV, are in a better agreement with the experimental results measured at the heavy-ion storage ring ESR than the Multi-Configuration Dirac-Fock calculations, especially at the resonance energy range close to the series limits. Graphical abstract: [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Physics is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• The study systematically investigated the wavelength distribution of transitions with principal quantum numbers (Δn=0,1,2) for Sn4+–Sn13+ ions in the wide spectral range of 6–45 nm and their contributions to the spectral profile. • Segmented simulations were conducted based on the assumptions of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model to explain the characteristics of the radiation spectra and variations in state parameters during laser-produced plasma expansion from the core to the outer periphery. • The short wavelength EUV spectra are simulated, and the difference of diagnostic state parameters reflects the non-uniformity of the plasma. The energy levels and transitions of highly charged Sn ions are key data for analyzing emission spectra, radiative opacity, and conversion efficiency of laser-produced Sn plasmas. Temporally–resolved spectra in the 6–45-nm range were acquired via high-precision, spatio–temporally resolved techniques. In addition, the Cowan code, based on Hartree–Fock multi-configurational interactions, was used to perform structural calculations for Sn4+–Sn13+ ion spectra. Emission spectra in the 11–18-nm range were primarily attributed to Sn8+–Sn12+ ions, with transitions involving principal quantum numbers Δn=0 and Δn=1. Whereas, emission spectra in the 6–11-nm and 18–45-nm ranges were mainly attributed to Sn9+–Sn13+and Sn4+– Sn9+ions, with transitions involving principal quantum numbers Δn=1,2. Furthermore, Segmented simulations were conducted based on the assumptions of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model to explain the characteristics of the radiation spectra and variations in state parameters variations during laser-produced plasma expansion from the core to the outer periphery. A specific analysis was conducted on the temporal evolution of the electron temperature and density, while the charge state of the plasma was analyzed over the 6–18-nm range. Based on the spectral diagnostics, this work focused on the impact of non-uniformity in the expansion of the Sn plasma. [ABSTRACT FROM AUTHOR]

• A systematic study of spatiotemporal evolution of extreme ultraviolet spectra in laser-produced silver (Ag) plasmas is performed with aid of a spatio-temporally resolved emission spectroscopy and multiconfiguration Hartree-Fock calculations. • Complex spectral structures were accurately revealed based on the assumption of a normalized Boltzmann distribution among the excited states and a steady-state collision-radiative model, which are dominated from the contributions of 4p and 4d excitations of Ag7+–Ag13+ ions. • Theoretical plasma-state parameters near the target surface at the initial stage of the laser-produced Ag plasma were determined via the steady-state collision-radiation model. Experimental and theoretical analyses are reported for the spatiotemporal evolution of extreme ultraviolet spectra in laser-produced silver (Ag) plasmas. The time-resolved spectra were acquired 1.5 mm from the target surface. The 4p and 4d excitations of Ag7+–Ag13+ ions were calculated with the aid of multiconfiguration Hartree-Fock calculations. The spectral line distributions of transitions in the dominant 4p and 4d excitation configurations and their variations with the degree of ionization were analyzed. Complex spectral structures were accurately revealed based on the assumption of a normalized Boltzmann distribution among the excited states and a steady-state collision-radiative model. Experimental peak origins were identified by comparing experimental and simulated spectra. These results will provide data for energy-level structures of highly-charged ions of middle- and high-Z elements and their radiative characteristics in plasmas. [ABSTRACT FROM AUTHOR]